chapter 3-9 ecology

chapter 3-9 ecology - Chapter 3-9 - Adaption to life in...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 3-9 - Adaption to life in varying environments Tuesday, November 06, 2007 12:55 AM Organisms maintain a constant internal environment An organism's ability to maintain constant internal conditions in the face of a varying  environment is called  homeostasis : o Homeostatic systems consist of  sensors effectors , and a  condition  maintained  constant o All homeostatic systems employ  negative feedback  - when the system deviates  from set point, various responses are activated to return system to set point.  Homeostatic system (model) Temperature Regulation: an Example of Homeostasis Principal classes of regulation: o Homeotherms  ("warm-blooded animals") - maintain relatively constant internal  temperatures o Poikilotherms  ("old-blooded animals") - tend to conform to external  temperatures Some poikilotherms can regulate internal temperatures behaviorally, and  are thus considered  ectotherms , while homeotherms are  endotherms Homeostasis is costly
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
As the difference between internal and external conditions increases, the cost of  maintaining constant internal conditions increases dramatically: o In homeotherms, the metabolic rate required to maintain temperature is directly  proportional to the difference between ambient and internal temperatures Limits to Homeothermy Homeotherms are limited in the extent to which they can maintain conditions different  from those in their surroundings: o Beyond some level of difference between ambient and internal, organism's  capacity to return internal conditions to norm is exceeded o Available energy may also be limiting, because regulation requires substantial  energy output Constrains on the Evolution of Homeothery Why is not every organism "warm blooded"? Being able to have constant temperature is function of size High effort to maintain temperature  in environments with high heat conductance Living in environments that do not provide enough food energy Partial Homeostasis  Some animals (and plants) may only be homeothermic at certain times or certain  tissues… o pythons maintain high temperatures when incubating eggs o Large fish may warm muscles or brain o Some moths and bees undergo pre-flight warm-up o Hummingbirds may reduce body temperature at night ( torpor ) Thermoregulation of Ectotherms Heat production as weapons (thermal defense) Honeybees kill  Vespa mandarina Conservation and Countercurrents Countercurrent fluxes can also assist in conservation of heat; here are two examples: o Birds of cold regions conserve heat through countercurrent circulation of blood in  legs Warm arterial blood moves toward feet Cooler venous blood returns to body core
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/29/2008 for the course ECOLOGY 380 taught by Professor Adams during the Spring '08 term at Rutgers.

Page1 / 6

chapter 3-9 ecology - Chapter 3-9 - Adaption to life in...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online